With the rapid development of camera systems and their application, especially in the area of safety technology, a closed camera systems (CCTV) and specific municipal surveillance systems are offered new opportunities for these systems work both day and therefore in good lighting conditions, and in night, possibly in much worse conditions (fog, rain), etc. This is made possible by the development of sensor characteristics chips in cameras and a new illumination options. For the realization of the need to evaluate the quality characteristics of different types of illumination, lights, working in different spectral bands, as well as specific cameras used in specific applications. This is the subject of this work.
REQUIREMENTS FOR illumination OF security camera
Illumination security cameras can be understood in several ways. The first option is a permanent lighting of scenes, such as the use of CCTV in the city where street lighting is a permanent lighting of the scene. Another option is to illuminate the scene in the visible spectrum only in the event of a disruption, and the light is then triggered in the simplest case, PIR detector, then a more complex scenario using the I&HAS and the character deter intruders. The last option is to illuminate scene with infrared light, where the contrary, we assume that the intruder will not illumination register and is therefore captured by CCTV without his knowledge. This is shown in the following Figure 1. According to standard EN 61341 - Method of measurement of luminous intensity in the main direction of the main radiation and the beam angle for reflector lamps. Measurement of this standard is difficult for technical equipment (eg photometric plate, etc.). Although the properties listed in the Standard requires relatively high-quality equipment for routine verification in practice to use a simpler method proposed in this work.
Sources of radiation
MEASUREMENT illumination BY wavelengths
To measure the spectral characteristics of the radiation sources was used spectroscope SpectroVis Plus with an optical probe made by Vernier.
Measurement characteristics of the LEDs in the visual and near infrared area
For measurement of LEDs was formed workplace, viz. Figure 2 Workplace consists of two current sources for the measured LED 1, which is used to set amperage according to the data sheet. LEDs emitted radiation incident on the optical probe 4 that the optical fiber transmits to 4 spectrometer and the measured value is transmitted through USB to a PC, where the result is displayed using SW. Optical probe and the measured LEDs are mounted on the axis in opaque plastic tube 5 due to interference from ambient light and radiation.
Figure 3 shows the spectral characteristics of the LEDs with the lowest and the highest wavelength.
Measurement results maxim 17 diodes are shown in Table 1.
The measured values show that the actual value of peak radiation not rated values specified in the data sheets, which implies that the selection of lamps for one radiator should have the same production batch, or to measure and divided into groups.
Measurements of the spectral characteristics of the individual sources of radiation
For measurement of LEDs was formed workplace, see Figure 4. Workplace consists of two power sources (typically 220 V mains switching relay interlocking systems) and its own radiation source 1 - glow. Sources of radiation incident on the optical probe 4 that the optical fiber transmits the processing into 4 spectrometer and the measured value is transmitted through USB to a PC, where the result is displayed using SW. Optical probe and measure the sources of glow are placed in wooden boxes covered with an opaque laminate 5 to avoid inaccurate measurements due to ambient light and radiation.
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The measurement results of all sources are listed in the following table.
MEASUREMENT OF REACH OF illumination
For the measurement range were chosen two methods. The first method consisted in measuring range using a light meter and the second method used the image of security cameras reflected from object.
Measurement of reach of illumination using light meter
To measure of range of illumination was used ALMEMO 2290-3 probe type A613 FL-VL. Distance measurement was selected in units of meters as follows: 1, 2, 5, 10, 15, 20, 25, 30, 35 and 40 m on Figure 13
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Measuring persistence with cameras
Figure 12 is an example of work. Source glow 1 is placed on a tripod and when connected to a power source transmits light into the hallway where the man 2, which represents an object - violators at a defined distance. From him the light bounces back and this radiation then processes the security camera 3, which is connected to a PC, where it will store the image.
As the source of the glow were used sources listed in Table 2
The next Figure we can see individual images combined reflector 500W halogen lamp and Pelco camera.
In terms of quality illumination is the result expected this:
- 500 W halogen reflector
- 120 W halogen reflector
- spot halogen lamp 50 W
- LED reflector
- LED spot light
- IR LED reflector
Conclusion
In conclusion we can say that the first step is to assess the scene and object properties that you want to record camera system. The second step is to select the appropriate illumination according to the application. In the third step, except for the resolution, which is determined by whether we want in the simplest case, the scene only to monitor the most demanding applications perform object recognition, it is necessary to define the spectral features of the camera and its sensitivity. Manufacturers often does not the data sensitivity cameras just in the infrared, which is very important for video surveillance systems that we want to implement so they are not easily identifiable. Generally, the illumination system is improved oversize than vice versa because the incorrect choice of illumination for the camera resulting from dysfunctional system.
BIBLIOGRAPHY
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Authors
Ing. Rudolf Drga, Ph.D., Tomas Bata University in Zlín, Faculty of Applied Informatics, Department of Security Engineering, Tomas Bata University in Zlín, nám. T. G. Masaryka 5555,760 01 Zlín, Czech Republic
Ing. Hana Charvátová, Ph.D., Tomas Bata University in Zlín, Faculty of Applied Informatics, Department of Automation and Control Engineering, Tomas Bata University in Zlín, nám. T. G. Masaryka 5555,760 01 Zlín, Czech Republic
prof. Ing. Dagmar Janáčová, CSc., Tomas Bata University in Zlín, Faculty of Applied Informatics, Department of Automation and Control Engineering, Tomas Bata University in Zlín, nám. T. G. Masaryka 5555,760 01 Zlín, Czech Republic
Vlastnosti zdrojů pro přísvit bezpečnostních kamer
Článek se zabývá technickým řešením přísvitu bezpečnostních kamer, principy měření záření ve světelné a infračervené oblasti. V praktické části jsou prezentovány výsledky měření s cílem vyhodnotit nejvýznamnější vlastnosti různých typů přísvitů, zdrojů osvětlení, které se využívají v bezpečnostních kamerových systémech.
